1 list as being super-toxic metals, most of these are associated with 



2 impurities in barium, and so are in a solid matrix, they are not readily 



3 exchangeable or easily leechable metals. 



4 They are not in the reducible phase that can be leeched off if the 



5 sediment becomes an oxic. Instead they are in the form of sulfide 



6 mineral inclusions in impure barite, or they are associated with the 



7 mineral lattice of clay material. Bentonite clay is the second most 



8 major ingredient in drilling fluids. 



9 So based on this, obviously, there is some concern, though, 



10 nevertheless, that you do have elevated levels in some drilling fluids 



11 and these could be a problem. One way to look at this is through 



12 bioaccumulation studies. 



13 Again, I mentioned earlier that cadmium and mercury are of 



14 particular concern to EPA, and as a result EPA has established 



15 guidelines for the maximum concentration of cadmium and mercury in 



16 drilling fluids. 



17 This is just a comparison of two barites, one with high trace 



18 metals and one with low trace metals, and then the kind of dilution or 



19 the concentrations you might see in sediments where you have barium 



20 accumulated from drilling muds. 



21 So, if the increment in barium in the sediments where you are 



22 monitoring is 100 ppm over background, which we did see in a few places 



23 on Georges Bank, then these are the expected concentrations of cadmium 



24 and mercury in that deposited drilling mud, if you had a very impure 



25 barite or if you had a very clean barite. 



26 You can see all these ones in the square here are below any 



27 expectation of detecting them above natural background. Generally 



28 cadmium in sediments--both cadmium and mercury in natural, clean 



29 sediments are rarely present at concentrations higher than about 1/10 



30 ppm. 



31 So, basically all these numbers within the block here are going to 



32 be undetectable in the environment. Only if you had an extremely high 



33 accumulation of barium from drilling mud and you had very dirty barite, 



93 



